Method and apparatus for volume control



May 28, 1935. s. RAMSEY 2,002,831

I METHOD AND APPARATUS FOR VOLUME CONTROL Filed Aug. 1 1929 2 Sheets-Sheet l AMPZ/F/B? 3: 5 1 W E 1 X 25 5:

INVENTOR May 28, 1935. G, RAMSEY 2,002,831

METHOD AI JD APPARATUS FOR VOLUME CONTROL Filed Aug. 1, 1929 2 Sheets-Sheet 2 INVENTOR V W M Patented May 28, 1935 METHOD AND APPARATUS FOR VOLUME CONTROL George Ramsey, Brooklyn, N. Y. Application August 1, 1929, Serial No. 382,767

17 Claims.

The present invention relates to volume control for sound records, broadcasting, telephony, etc.

In picking up sounds by microphone and translating the audible wave into an electric wave which may be utilized formaking a record on a film, phonograph disc, radio broadcasting, telephony, or other purposes, it frequently happens that the sound energy or volume intensity at times exceeds the operating limitsof the apparatus. When this happens a condition referred to in the art as blast occurs and this badly dis-. torts the sound wave and produc'esvery undesirable results. his now common in the art to attempt to manually control the current from the microphone in such manner as to avoid this undesirable condition. It is frequently inconvenient to properly manually control the' current and undesirable results are often obtained. Furthermore, a personal element enters'to such an extent that frequently a program or record is spoiled. This often occurs where a singer with a very powerful voice becomes enthused in an artistic efiort and sings with such volume that the operator unduly cuts down the volume, thereby distorting and destroying the artistic effect.

The present invention relates'to 'mec'hanisms and devices whereby the operation of themicrophone circuit is automatically controlled so that the desired results are automatically obtained. By the term microphone circuit used herein it is to be understood that any circuit carrying the audible frequency waves is to be included, either in receiving theoriginal sound or inreproducing the sound from records, or from a receiving apthe invention.

paratus. 'It may be the circuit directly including the microphone or some circuit more or less remote therefrom over which the audible waves are carried. In other words, it is intended to control the volume output to the final stage of recording or broadcasting or telephony, or the re production of the sound from electrical waves;

Other and further objects of the present invention will in part be obvious and will inpart be pointed out hereinafter by reference to the accompanying drawings wherein theinve'ntion is disclosed more or less diagrammatically.

It is realized that the present invention may be embodied in constructions and carried out by steps other than those herein specifically dis- '7 closed and without departingfrom the invention.

Therefore, it is to be understood that the dis-. closure is illustrative and not to be considered in the limiting sense.

' Fig. 1 illustrates one apparatus for carrying out Fig. 2 illustrates the operation of the tubes in the control circuit in Fig. 1. i

Fig. 3 illustrates the eiiective operation on waves of audible frequency of the apparatus shown in Fig. 1.

Fig. 4 illustrates the resultant audible frequency wave.

Fig. 5 illustrates another method of carrying out the present invention.

Fig. 1 illustrates diagrammatically an electrical device for carrying out the present method, and may be used either in transmitting or. receiving apparatus, and wherein the current from the microphone is passed to the primary E of a transformer having two secondary windings l2 and M. The voltage from one of the secondary windings is delivered through a potentiometer i to the input of amplifierlfi. The voltage from the other secondary winding I4 is delivered to the input of a pair of three electrode tubes I? and 3 connected in push-pull relationship. The alternating component of the output of tubes I1 and [B is impressed by means of transformer 19 across the portion n of potentiometer l5.

' Tubes l1 and I8 may have a grid voltage plate current characteristic such as shown in Fig. 2. C-battery 20 is connected into the grid circuits ofthese two tubes I! and I8 and is of 'sufiicient strength to maintain the grids at a potential below E1 until the maximum desired voltage has been impressed upon the amplifier. The connections are such that. Ey is 180 degrees out of phase with E5. As long as EX is below the maximum desired amount, the grid voltage of tubes I1 and i8 is below E1 and hence virtually no current flows through the secondary of transformer 19. Accordingly Ey is zero, and the voltage impressed upon the 'amplifier'is EX. When the microphone current'increases above the maximum desired amount the grid voltage of tubes ii and I8 rises above value E1, i. e., on one half cycle the grid voltage on tube IT is above E1 and on the other half cycle the grid voltage of tube i3 is above E1. Accordingly, current will flow in the plate circuits of tubes [1 and i8 and this current will cause a voltage Ey to be impressed upon the potentiometer-I5, which voltage is 180 degrees out of phase with EX. The relationship of voltagies E; and B is shown in Fig. 3. The resultant of these voltages Er shown in Fig. 4 will then be impressed upon the input circuit of the amplifier. Accordingly when the microphone current rises above the maximum desired value the circuit operates to automatically limit the voltage that is impressed upon the input circuit of the, amplifier, and thus retains the amplitude of the waves in the output circuit below the predetermined limit.

Referring now more especially toFig. 5, which also may be used either in transmitting or reproducing circuits, the tube 253 is kept blocked by the C-battery 2! as long as the microphone current in the circuit 22 is below the predetermined maximum or" voltage Ex. When the voltage in the microphone current in circuit 22 is below the maximum, the value of the current in Ey is zero, and therefore the voltage impressed on the tube 24 is EX, which corresponds to the full microphone current. When the microphone current increases above the allowable maximum, then the tube sets up a voltage Ey. The transformer windings 25 and 25 are connected so that the'voltage Ey opposes the voltage Ex. The voltage imposedson the input circuit or tube 24 is therefore Ex-Ey. Ittherefore will be seen that the control does not become effective until the maximum wave amplitude allowed is reached and then the control does become eiiective so that the resultant current is below the predetermined maximum. A potentiometer 2"! is arranged in the input circuit 28 which leads to amplifiers in the final operation apparatus whereby the current may be led to telephone line, broadcasting, recording instruments, or other apparatus for purposes desired. This potentiometer permits control of the final circuit leaving the volume control apparatus above specified.

From the foregoing, it will be observed that the present invention comprises a method and means whereby the voltage or amplitude of oscillating waves is controlled within limits whereby excessive voltage, or wave amplitude is prevented. While the drawings refer to the incoming current as a microphone current, it is to be understood that this term is intended to cover a current either at a sending station or at a receiving station.

Having described my invention, I claim:

' 1. In a device of the class described, the combination of an input circuit and an output circuit, a main circuit connecting said input circuit and said output circuit, and an auxiliary circuit operativ'ely connected with said input circuit and said main circuit, and means in said auxiliary circuit to impose an inverted wave of the same frequency of low amplitude upon a portion of said main circuit to control the amplitude of waves in said main circuit.

2. In a device of the class described, an input circuit and an output circuit, a main circuit operatively connecting said input circuit and said output circuit, an electronic device in said main circuit, an auxiliary circuit operatively connected with said input circuit and said main circuit, a

second electronic device in said auxiliary circuit,

biasing means blocking the electronic device in the auxiliary circuit when the amplitude of waves in said input circuit are below a predetermined amount, said auxiliary circuit being operative to produce in the main circuit a voltage opposed to the input voltage at all times when the voltage in said input circuit exceeds the predetermined amount in order to limit the voltage in said output circuit. 1 3. In a device of the class described, an input circuit, an output circuit, a main circuit between said input circuit and said output circuit, an auxiliary control circuit, a vacuum tube insaid auxiliary control circuit, means to impose a blocking voltage of predetermined magnitude on said vacuum tube whereby said auxiliary control circuit is unblocked to produce an opposed voltage in the main circuit at all times when the voltage in the input circuit exceeds a predetermined amount.

4. Apparatus of the character described comprising a source of impulses, an electric discharge device having its input electrically connected to said source, a shunt circuit interposed between said source and the input of said discharge device, and means in said shunt circuit for generating in the output thereof impulses of relatively low amplitude upon the introduction into the shunt circuit of impulses exceeding a predetermined amplitude limit, the impulses introduced into the input of said discharge device from said shunt circuit being opposite in phase to the impulses introduced thereinto from said source.

5. Apparatus of the character described comprising a source of impulses, an electric discharge device having its input electrically connected to said source, a shunt impulse supply circuit interposed between said source. and the input of said discharge device and including means for shifting the phase of impulses from said source, and means in shunt circuit for rendering the same inoperative to supply impulses to the input of said discharge device when the impulses: introduced into the shunt circuit are below a predetermined amplitude.

6. The method of reducing excessive wave amplitude of an electrical current in a connecting circuit between an input circuit and an output circuit, said method comprising inverting the excessive portion of the wave from the input circuit and applying said inverted portion to the wave in the connecting circuit to reduce the amplitude of the same wave in the output circuit.

7. The method of reducing excessive wave amplitude of an electrical current in a connecting circuit between an input circuit and an output circuit, said method comprising establishing a maximum wave amplitude which shall pass through said connecting circuit without being controlled, taking the excessive portion of a wave above said maximum, inverting the same and applying the inverted portion to said wave as an opposing voltage to reduce the amplitude of the said wave in the connecting circuit.

8. The method of reducing excessive wave amplitude of an incoming electrical current in a connecting circuit between an input circuit and an output circuit comprising producing an opposing current, of the same frequency and inverted in wave form, blocking said opposing current until the wave amplitude of said incoming current reaches a predetermined maximum, and releasing the opposing current into the connecting circuit in the proportion that the wave amplitude of the incoming current exceeds said maximum.

9. The method of controlling the wave amplitude of an electrical current in a connecting circuit between an input circuit and an output circuit, said method comprising imposing the portion of a wave beyond a predetermined magnitude in inverted form in the input circuit in opposition to said wave in the connecting circuit to reduce the amplitude of the same wave in the output circuit.

10. The method of limiting the amplitude of the output of an electronic device which comprises supplying primary impulses to the input of said device, and introducing impulses of inverted wave form of less magnitude than the primary impulses to the input of said device when said primary impulses are of such order of amplitude as to raise the output amplitude above the fixed limit.

11. The method of limiting the amplitude of an amplifying circuit which comprises supplying primary impulses to the input of said amplifying circuit and automatically supplying secondary impulses of similar but inverted form of less magnitude than the primary impulses to the input of said amplifying circuit when the amplitude of the first primary impulses exceeds a predetermined limit.

12. In a device of the class described, an input circuit adapted to receive oscillatory impulses, an output circuit, a main circuit comprising an electronic amplifier tube having a grid and a plate connected in circuit between the input circuit and the output circuit, and means comprising an auxiliary control circuit operatively connected with the input circuit and adapted to apply an opposing oscillatory voltage to said grid in the main circuit when the amplitude of the waves in the input circuit exceeds a predetermined limit to control the amplitude of the waves in the output circuit.

13. In a device of the class described, an input circuit adapted to receive incoming oscillating impulses, an output circuit, a main circuit having an electronicvalve between the input circuit and the output circuit, and dampening means adapted to produce oscillatory impulses comprising an inverted form of the incoming impulses and to apply the same to the main circuit to dampen undesirable oscillations therein.

14. In a device of the class described, an input circuit carrying incoming signals, an output circuit, a main circuit between the input circuit and the output circuit, said main circuit comprising an electronic device having electrodes comprising terminals for the discharge through said device, means to control the discharge through said device by applying an inverted signal voltage to one of said electrodes to oppose the voltage of the incoming signal to limit the amplitude of the waves in the output circuit while maintaining the operation of said device within its non-distortional zone of operations.

15. In a device of the class described, an input circuit to receive oscillatory impulses, an output circuit, an electronic tube in an intermediate circuit between said input and said output circuits, control means, and means to render the control means effective when the wave strength exceeds a predetermined limit, said control means producing a control voltage operative to control the efiective operation of said tube while maintaining the operation of said tube in the same position on its operating characteristics within the distortionless zone or tube operations to transmit a wave which does not exceed a predetermined amplitude.

16. In a device of the class described, an input circuit to receive oscillatory electric impulses, an output circuit, an electronic device in an intermediate circuit between the input and output circuits, and control means producing an inverted portion of the received oscillatory electric impulses to provide acontrol voltage operative to control the operation of the electronic device within maximum limits in the distortionless zone of operations of the electronic device to retain the amplitude of waves in the output from the electronic device below a predetermined maximum limit.

17. A device of the class described comprising an input circuit to receive oscillatory impulses, an output circuit, and control means between said circuits to impose on the received oscillatory impulses inverted oscillatory impulses corresponding to an inverted form of undesirable received impulses in the input circuit to cancel said undesirable impulses coming through said input circuit.

GEORGE RAMSEY. 

